Hybrid Relays?

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JohnTheBrewist

JohnTheBrewist

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Hey all, I guess this is a strange first post, but I've been lurking here for a while... Especially in the Electric Brewing section. You guys are a true inspiration!

I've begun a project to build a brewshed and electric brewery for 10 Gal batches. I've assembled most of the parts for the control panel, and while searching for relays, I came across these hybrid SSR/EM relays. They are good for millions of cycles and don't require a heatsink. They are a little expensive, but less than the cost of an SSRD.

I'll have two 5500 Watt elements controlled by a 3-way switch, PIDs and Relays similar to Kal's setup. I was thinking to use 4 of these relays. Two w/ 120VAC control for on/off switching, and two w/ DC control for PID input.

I'd appreciate any thoughts on this.

Thanks,

Moose
 
Wow, those are large.

What is the reason you are leaning towards these relays? Is it just because of the heat generated by an SSR?

As a cost savings idea, it seems like the 120V versions that you are describing for use as main power switches cold just as well be implemented with definite purpose contactors. You won't be manually flipping the kill switches that often, so spending $165 on two of these relays when you could just spend $30 on a couple of 120V coil contactors seems like a more cost effective solution.
 
Thanks for the quick reply! Yes, they do take up some space. In actuality, I'll probably use something like this Magnecraft relay for the on/off switching since I'm planning to mount most things on DIN rails.

I'd guess the only reason I considered the hybrid relays for on/off control is that they are quiet like SSRs but don't generate the heat. On the PID side, if I go with SSRs, I may go with two for each element for the belt and suspenders approach. I've seen a lot of comments about SSRs failing closed and the hybrids seem like they might be a bit more reliable (but I can't really say what gives me that impression).

These hybrid relays just caught my interest, so I thought I'd run 'em the flagpole. Don't really know if I'd spare the extra expense.

Moose
 
MenkeMoose said:
On the PID side, if I go with SSRs, I may go with two for each element for the belt and suspenders approach. I've seen a lot of comments about SSRs failing closed
Click to expand...

You know what? Most of the comments I've seen about them failing closed are on this forum and are mainly people just repeating that they heard that it is common for them fail that way. :D I asked if anyone had actually had one fail on them and fail in the closed position, and I don't think anyone raised their hand.

It may or may not be true, but that 'fact' seems to quickly be turning into another homebrewing boogeyman, like hot-side aeration, autolysis in 4 weeks, etc.
 
Walker said:
You know what? Most of the comments I've seen about them failing closed are on this forum and are mainly people just repeating that they heard that it is common for them fail that way. :D I asked if anyone had actually had one fail on them and fail in the closed position, and I don't think anyone raised their hand.

It may or may not be true, but that 'fact' seems to quickly be turning into another homebrewing boogeyman, like hot-side aeration, autolysis in 4 weeks, etc.
Click to expand...

I have not had a SSR fail, so I can't say if open or closed is more likely.

I will say this though... I'm not going to put myself in a position on a regular basis to get fried if a SSR happens to fail closed.

I realize there is a very small chance I could have my panel open, then stumble into it and put my hand on a bare contact at the same time a SSR failed closed and I could get zapped, But really, you're talking about protecting equipment.

I have a SSR on each leg of my 220v elements, so BOTH would have to fail closed for the element to be at risk and I think I have gone as far as I care to protect a $25 heating element.

Just my .02
 
we're a little :off:, but....

I'd say that the SSR(s) isn't(aren't) there to "protect" anything. It(they) is(are) there for control only. If I am ever going to touch the heater element, I flip the kill switch and cut the voltage off completely. I never rely on the SSR when my safety is concerned, and I never rely on the SSR when the kettle is empty. I flip that kill switch to the OFF position for those times.

I use a single SSR. If it fails in the closed state, the worst that can happen is that my mash overheats or my boil is too strong. I've wired the back of my PID (using the normally closed alarm relay built into it) to prevent an overheated mash - if the heat gets too high, the control signal to my contactor is broken and the element powers down completely. The boil, i couldn't do anything about but just let it run strong, which would still give me beer, I just might have to add some top-off water at the end and be mindful of a boilover.
 
I found this interesting article on SSR failure stating that SSRs are likely to fail closed if they fail. But it also states that heat is the prime factor causing failure.

I bought a giant 7"x11"x4" 9lb heatsink on ebay that I'll use, if i use SSRs-- should keep them cool enough.

So it still seems that the Hybrid relay might be less likely to fail since the heat issue isn't ther to begin with.
 
Walker said:
we're a little :off:, but....

I'd say that the SSR(s) isn't(aren't) there to "protect" anything. It(they) is(are) there for control only. If I am ever going to touch the heater element, I flip the kill switch and cut the voltage off completely. I never rely on the SSR when my safety is concerned, and I never rely on the SSR when the kettle is empty. I flip that kill switch to the OFF position for those times.

I use a single SSR. If it fails in the closed state, the worst that can happen is that my mash overheats or my boil is too strong. I've wired the back of my PID (using the normally closed alarm relay built into it) to prevent an overheated mash - if the heat gets too high, the control signal to my contactor is broken and the element powers down completely. The boil, i couldn't do anything about but just let it run strong, which would still give me beer, I just might have to add some top-off water at the end and be mindful of a boilover.
Click to expand...

My response was related to the OP's concern about a SSR failing closed.

In my long winded way, I was trying to say, don't count on a SSR for safety.

If it fails closed, and you don't notice, you could ruin a batch of beer or a heating element. Both of which are probably less expensive than using the Hybrid Relays in the original link.
 
Walker said:
I'd say that the SSR(s) isn't(aren't) there to "protect" anything. It(they) is(are) there for control only. If I am ever going to touch the heater element, I flip the kill switch and cut the voltage off completely. I never rely on the SSR when my safety is concerned, and I never rely on the SSR when the kettle is empty. I flip that kill switch to the OFF position for those times.
Click to expand...

The voice of reason, Walker. The SSR is not a safety device. Just because the dual SSRs are off it does not mean it is safe to touch the heater terminals. It is in fact most unsafe. There should always be a contactor or big switch feeding the SSR anyway, and the only safe way to mess with the heater is with that switch off. Better yet unplug the whole thing.

I wonder if we aren't in fact inviting failure by having two SSRs per heater. I would guess that the MTBF (mean time between failures) would go down if we add a second SSR.

If I were to send my brewery on a unmanned trip around the moon I would probably have dual (or quad) SSRs, but when brewing at home I will be watching the temperature readouts and it would not get away from me by even 10 degrees.
 

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